1. Field of the Invention
The present invention relates to the use of radioactive sources to treat diseases of the body. More particularly, the present invention relates to the use of a flexible member housing a radioactive source for the temporary delivery of radiation to treat diseases of the body.
2. Description of the Prior Art
Radiation is used to treat cancer and other diseases of the body. Radiation has long been proven to destroy fast multiplying cells (e.g., cancer) in hopes of destroying or preventing the spread of the disease. Brachytherapy, which is the treatment of cancer at close distances, is one example of the use of radiation for treating diseases of the body. During brachytherapy, a radioactive source or sources are positioned in the area needing treatment. Depending on the shape, size and delivery means of the radioactive sources, the sources are either kept permanently in the body or removed after a specific amount of time. Since permanent implants are tiny seeds approximately 3 mm long and 0.5 mm wide, the use of these seeds do not relate to the present invention. Consequently, the focus of this application will be on the field of temporary implants.
The term temporary implants describes the procedure of maneuvering a radioactive source or sources to the treatment site utilizing a transport catheter or tube which has been previously placed in the vicinity of this treatment site. Alternatively, the transport catheter and temporary implant can simultaneously be maneuvered to the treatment site. In either situation, after a specified period of time, these sources and the transport catheter or tube are removed from the body. Since the radioactive source or sources may encounter a tortuous path in various arteries, veins, ducts, or the like inside the body to reach the treatment site, the radioactive source is usually attached by some device to a flexible drive member. This source and the drive member may be used many times, and, therefor must be able to withstand the many bends it encounters when it is maneuvered to the treatment site or removed therefrom, without breaking.
There are several devices on the market in which radioactive sources are attached to flexible drive members. Each of these devices is constructed in a different fashion and each has its limitations. Examples of these prior art devices are described in U.S. Pat. No. 4,819,618 and 5,141,486, both issued to Liprie as well as U.S. Pat. No. 4,861,520 issued to van't Hooft. The two Liprie patents describe a radioactive element which is attached to a drive member by means of a junction welded to the drive cable. The patent to van't Hooft describes an apparatus which attaches radioactive sources to a drive cable by means of a stiff capsule welded into the end of the cable. Since the most resistive portion to flection of any flexible material, such as a cable, tube, or wire is the segment closest to the end, to join a capsule which is stiffer than this material and welded onto its end would only add to the resistance to bending and would adversely effect maneuvering the material through the body.
U.S. Pat. No. 5,084,002 issued to Liprie describes an ultra-thin high dose iridium source included within an oversized hole drilled inside the end of a solid platinum wire. The whole assembly is then drawn down to the desired diameter of the wire. While this patent does not describe the situation in which a radioactive source is joined to the end of a solid cable, the platinum delivery wire would still present problems with respect to maneuvering the wire through the numeral twists and turns in the body.
Finally, U.S. Pat. No. 5,282,781 issued to Liprie employs a tube, a backbone wire, a pure iridium core and a plug and draws down the entire assembly to form a tight seal between the housing material and the backbone wire and the plug. Without this drawing down of the housing onto the backbone wire, radioactive flakes from the core would migrate throughout the inside of the assembly wire, resulting in unwanted contamination. This "drawing down" step would increase the costs and difficulty of manufacturing the source wire.